1. Field of the Invention
The present invention relates to a material for use in currency and currency made therefrom. More particularly, the invention includes an antimicrobial polymer material which can be used in the manufacture of banknotes having security features therein.
2. Prior Art
Banknotes historically have been constructed of a paper or a paper-like fabric. Currency paper in the United States, for example, is composed of 25% linen and 75% cotton. Presently, some countries are experimenting with a “paper” banknote made in whole or in part of one or more polymers. Australia, Mexico, Brazil, Indonesia and China are among the nations testing or rolling out polymer-based banknotes.
Over the course of a banknote's life, it is handled by countless individuals. In addition to handling, banknotes are routinely placed in pockets, purses, wallets, socks and other containers/locations where microbes can be found and can grow.
The likelihood of a banknote becoming contaminated with microbes is very high, as confirmed by culturing and plating of used banknotes. Bacteria can readily colonize on fiber-based and even polymer banknotes, facilitating cross-contamination and the spread of infections and/or diseases. Even were the banknote constructed wholly of one or more conventional polymers on which microbes do not traditionally flourish, such microbes certainly could survive thereon and be transmitted from one person to the next.
Banknotes typically include a number of security features to prevent counterfeiting. Specialized fibers may be interwoven into the fabric of the banknote. Red and blue fibers have long been an ingredient of U.S. paper currency. Special features such as these fibers are embedded in currency paper to ensure that reproduction is difficult. While some counterfeiters attempt to draw these fibers onto the surface of the bill, close inspection reveals the absence of the authentic embedded fiber and the clear presence of crude lines drawn on the surface. Prior to approximately 1941, such anti-counterfeit fibers were silk. Presently, red and blue synthetic fibers of various lengths are distributed evenly throughout the paper.
Security threads are useful anti-counterfeiting features and now run the width of U.S. paper currency. In some early versions of U.S. paper currency, thin security threads were added to paper. In these currencies, the number of threads in the paper represented a specific denomination. Continuing with example of U.S paper currency, the thread for the modern $100 bill bears the phrase “USA 100”. This thread print also can only be seen with transmitted light, which makes photocopy-based counterfeiting impossible.
In addition, new U.S. security threads glow red when held over ultraviolet light. Other printed features can include inks comprising metallic flakes or particles, holographic images, and the like. These features give the printed element a visual aspect that cannot readily be xerographically or otherwise reproduced.
Banknotes also may have a watermark added thereto. A watermark is created during the paper banknote making process and is caused by variations in the density of the paper. As light passes through the tiny variations in thickness, different light tones are observed. These varying tones form a clear image when held up to transmitted light.
One key requirement of an antimicrobial or bactericidal banknote is the antimicrobial additive must not materially affect key properties of the banknotes, such as durability or one or more of the security measures as discussed above.